University of Vermont Extension 
Department of Plant and Soil Science

Fall Article

PLANTING MUMS AND OTHER SEPTEMBER GARDENING TIPS

By Dr. Vern Grubinger, Extension Vegetable Specialist
Dr. Leonard Perry, Extension Professor

September is back-to-school time.  Just as you wouldn't send your kids off to school unprepared, neither should you ignore the needs of your garden as it heads into fall.  Gardens need special care to help prepare them for winter and for the next growing season.

In the vegetable garden, harvest onions once tops have fallen over and the necks have started to dry down and shrink just above the bulb.  Pull up bygone plantings of beans, broccoli, and other crops that have been harvested. Removal of crop  residues is important to disease and insect prevention as it takes away the places where pests and diseases can overwinter.  Remove any weeds you missed earlier before they set seed and cause problems for the next growing season.

If frost threatens, cover tomatoes, peppers, and salad crops with a double layer of plastic. Don't worry about your carrots,  turnips, and parsnips. They'll actually taste sweeter after being exposed to temperatures between 28 and 34  degrees F. For harvest in early winter, cover these root crops with 18 inches of straw, hay, or dry leaves. This will keep the ground from freezing so deeply and make it easier to dig them up.

Cover crops are a great way to hold precious topsoil in place over the winter, and they add organic matter, too.  An  excellent fall cover crop for home gardens in northern New England is oats. This crop can be sown anytime in September.  It is inexpensive and will reliably winter-kill so next spring all that remains is the dead residue, which is much easier to incorporate into the soil than rye.

After removing residues, rough up the soil surface then lightly rake in at least four or five pounds of oats per 1,000 square  feet.   Higher rates will give an even thicker cover crop, which helps with weed suppression.  Use certified seed or  triple-cleaned feed oats to assure that the seed is free from weed contamination.

In flower gardens, clean up residue from plants infected with powdery mildew.  The disease will overwinter on stems and  foliage, creating a source of spores for new infections next year.  Rake dead leaves from under rose bushes.  Decaying  leaves may provide a conducive breeding ground for fungus and insects that will prey on next year's roses.

For an instant garden and a blast of color as summer turns into fall, fill your flowerbeds and empty spaces in your  landscape with chrysanthemums.  They come in a wide range of autumn colors from white, yellow, and gold to bronze and maroon.  Lighter colors tend to bloom earlier than the darker reds and purples, so select different colors for a longer display of color.

What's nice about mums, in addition to the long bloom time, is that they can be transplanted while in full bloom.  Just be  sure to water thoroughly until they become established. Most garden mums are not reliably hardy in most northern areas, so enjoy them this fall, but don't expect them to overwinter well.

Mums also work well as container plants to decorate patios, porches, and decks.  Go easy on the water, however, to  prevent root rot.  Potted mums probably will not do well inside as lower light levels often result in yellowing leaves and  droopy flowers.

Flowering kale and cabbage also make nice fall plants to replace annual flowers.  Both will turn a beautiful color with the cold and will last until covered with snow.  Or try fall asters, which are grown in pots by many garden centers for sale at this  time of year.  They provide good color, and many are hardy as well.

This is a good time to evaluate your autumn landscape to see where new plants can be added next spring and summer to  provide fall color.  Asters, perennial salvias, and some of the sedums (including the popular 'Autumn Joy' with its attractive  pink flowers) are good choices for long-lasting color at this time of the year.   Or consider New York asters (one to two feet high) and the taller New England asters (three to five feet), or if moist soil and a sunny spot, Helen's Flower  (Helenium) cultivars with fall colors of reds, oranges, and yellows.

Goldenrod is another possibility.  There are many nice cultivars, including 'Golden Fleece,' which grows to a low, uniform height of two feet.  Contrary to popular belief, goldenrod doesn't cause allergies.  Rather it's the ragweed, which is out at  the same time.

You can still plant shrubs and trees this month since their roots will continue to grow into November, giving them plenty of  time to get well-established before winter. You might find some good clearance sales this time of year, but don't let price  dictate what you buy.  Leftovers at the end of the season can often be just that.  Poor quality means they might require more  help to survive.  Choose varieties that will do well in the hardiness zone where you live, as well as fit into the space  you have available.  Allow ample room for growth as trees and shrubs mature.

With the cooler days of early fall, grass growth speeds up (and slows down later in fall with colder temperatures), so keep  mowing as long as it is growing.  Set the blades to cut grass at least two inches high.

If your lawn has more than a half-inch of thatch (mat of partially decomposed grass stems and roots), remove the build-up  as it will interfere with the flow of nutrients, water, and air to the roots.  Thatch also may harbor plant diseases and insects.  To remove, use a dethatching machine, which is sometimes called a verticutter.  You can rent one from many rental agencies.  Or hire a professional contractor to do the work.

It's okay to fertilize grass in the early fall.  By the same token, late season fertilizer applications will help herbaceous  perennials overwinter better.

Start a new compost pile, adding grass clippings, spent annuals, and leaves that you've raked.  Leaves are a very good  source of carbon, and they help to soak up excess water, so you may want to shred some with the lawnmower and stockpile in a garbage can for composting food wastes over the winter.

Shredding leaves will help them break down more quickly and make them more absorbent. Weeds from the garden also  may be added to the pile, provided they are not full of seed heads. Even though composting can kill off weed seeds, most home compost piles do not get hot enough to assure this.

Since an outdoor compost pile won't be very active in the coldest winter months, you can let red worms do your  composting in your basement.  Start by getting a large wooden box or plastic bin with air holes and a cover.  Fill it half way with well-moistened, shredded, plain newspaper or leaves.  Add about a pound of red worms, ordered from a worm farm  or garden supply catalog, or collected from an old manure or compost pile. Then you're ready to add vegetable  scraps from your kitchen, but no more than about half a pound per day.  Be sure to bury the scraps completely, and avoid really tough materials like corn cobs and nut shells.

Other September activities: attend a fall harvest festival or late season agricultural fair; mulch asparagus beds with a thick,  loose layer of hay; go apple picking.


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